SK37789A3 - Device for record control of information into storage track of optically readable record carrier - Google Patents

Abstract

A method of and apparatus (Fig. 4) for recording an information signal (Vi), in particular an EFM-modulated signal, are revealed, which information signal comprises time-code signals which alternate with first time-synchronisation signals. The record carrier (1) which is employed is provided with a preformed servo track (4) which exhibits a periodic track modulation whose frequency is modulated in conformity with the position-information signal (Fig. 2). The position-information signal (Fig. 2) comprises position-code signals (12) which alternate with position-synchronisation signals (11). During recording a fixed phase relationship between the time-synchronisation signals and the position-synchronisation signals (11) is maintained, so that the portion (141) of the servo track (4) in which the time-synchronisation signals are recorded are situated at fixed positions relative to the servo-track portions (140) which represent the position-synchronisation signals (11).

Description

Technique area

The present invention relates to an apparatus for recording an information signal into a track of an optically readable record carrier.

BACKGROUND OF THE INVENTION

A device for recording a digital information signal is known, for example from U.S. Pat. No. 4,473,829. The device described herein uses a carrier provided with a preformed track divided into synchronization sections and information recording sections, the two sections alternating with each other. The information recording sections are intended for recording the information signal. In these sections, the track exhibits periodic modulation with a constant frequency. During tracking, a clock signal can be derived to control the recording process.

The synchronization sections include the address of the adjacent information recording section in the form of pre-recorded combinations of record marks. This address information allows you to quickly and accurately determine the location of a portion of a track.

However, the carrier used in the known device is not very suitable for recording signals in an EFM code according to the CD-Audio or CD-ROM standard. Indeed, an uninterrupted area for recording information is required to record such signals. The known device corresponds to the drawbacks of this record carrier.

SUMMARY OF THE INVENTION

[0008] The present invention eliminates the problem of an apparatus for controlling the recording of information in a track of an optically readable record carrier comprising a radiation sensitive recording layer disposed on a disc substrate, the track having a periodically wavy line corresponding to the amplitude of the periodic signal whose frequency is modulated by a digital position information signal. a corresponding portion of the recorded information along the track length, the wavy line comprising first portions in which the ripple has a first predetermined period alternating with second portions in which the ripple has a predetermined second period, wherein the ripples with the first and second periods are assembled after the length of the track into alternating combinations corresponding to a position information signal and a synchronization signal, the device comprising a clock signal generation circuit, the output of which the up is connected to the clock input of the information recording modulation circuit, and further comprises a phase detector, the first input of which is connected to the second output of the clock signal generating circuit and the second input of the phase detector is connected to the optical detector output of the optical recording head a recording beam, wherein the output of the phase detector is connected to the drive circuit of the record carrier drive motor.

Such a device is more suitable for recording signals in an EFM code and allows accurate positioning of part of the track that does not yet contain an information signal. Maintaining a solid phase relationship between the phase detector input signals has the advantage that, after recording, the first and second synchronization signals remain synchronized for the entire recorded information signal. Thus, it is possible to use the time code signals contained in the information signal and the position code information signals produced by the modulation of the track to determine the position of the track portion at which a portion of the information signal has been recorded, giving a highly flexible system for determining the position of a portion of the recorded signal.

In practice, it appears that when the record carrier has defects, for example, it is scratched, the phase relationship between the two synchronization signals can slowly change as a result of the failures caused by said scratch. To alleviate this drawback, the device according to a further feature of the invention is adapted so that the optical head detector of the recording head is connected via its input to a demo circuit with output of sync position codes connected to the control unit, further provided with time sync codes. connected to the time synchronization code input and the position synchronization code input, the output of the phase comparator being connected to the driver circuit.

If several different adjacent information signals have been recorded on the record carrier, it is desirable to ensure that there is always a solid phase relationship between the time code signals and the position code signals so that certain portions of the information signal can be located by both code signals. The device according to the invention allows the position information signal represented by the track section at which the information signal recording begins to be determined by detecting track modulation, wherein the time code signals are adapted to the position code information signal thus determined.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in more detail by way of example with reference to the accompanying drawings, in which:

Fig. 1 shows schematic form marks of a record carrier used in the device according to the invention,

Fig. 2 shows a graph of the position information signal;

Fig. 2a a diagram explaining the purpose of the ripple in the track,

Fig. 3 is a graphical representation of a suitable location information code format;

Fig. 5a and 12 show the flowcharts of the microcomputer programs used in the apparatus of the invention

Fig. 6 is a block diagram of an example of a demodulator used in an apparatus according to the invention;

Fig. 7 shows a detail of a portion of the created track with a combination of recording marks on a substantially enlarged scale;

Fig. 8 is a block diagram of a record carrier manufacturing apparatus for use in a device according to the invention;

Fig. 9 is a block diagram of an exemplary modulation circuit for use in the apparatus of FIG. 8

Fig. 10 is a graphical representation of several signals appearing in the modulation circuit as a function of time t a

Fig. 11 is a graphical representation of the position synchronization time signals of the recorded signal relative to the pre-recorded position synchronization signals in the servo track.

DETAILED DESCRIPTION OF THE INVENTION

The embodiment described below is particularly advantageous for recording EFM signals in accordance with the CD-Audio or CD-ROM standard. However, the invention is not limited to these embodiments.

Before describing an embodiment of the invention, a brief description will be made of those characteristics of the EFM modulated signal that are important for a proper understanding of the invention. The EFM signal comprises secondary code frames, each consisting of 98 EFM signal frames. Each EFM signal frame includes 588 channel bits of the EFM signal. The first 24 bits of these 588 channel bits are used for a frame synchronization code that includes a code combination that can be distinguished from the rest of the EFM signal, and the other 564 channel bits of the EFM signal are arranged as 14-bit EFM symbols. The synchronization code and EFM symbols are each separated by three connection bits. The available EFM signal symbols are divided into 24 data symbols, each representing 8 bits of the unencoded signal, 8 parity error correction symbols, and one pilot symbol representing 8 control bits. The 8 bits represented by each EFM control symbol are designated by P, Q, R, S, T, U, V, W bits, each of which has a fixed bit position. The 16 bits of the EFM control symbols in the first two EFM frames of each subcode frame form a sync signal of the subcode indicating its start. The remaining 96 bits Q of the 96 remaining frames of the EFM signal form the Q-channel of the secondary code. Of these bits, 24 bits are used to indicate the absolute time code. This absolute time code indicates the time elapsed since the start of the EFM signal. This time is expressed in minutes (8 bits), seconds (8 bits) and auxiliary code (8 bits).

Furthermore, it should be noted that the EFM signal code is devoid of a unidirectional component, which means that the EFM frequency spectrum hardly shows any frequency components in the frequency range below 100 kHz.

Figure 1 shows an embodiment of the carrier 1, wherein Figure 1a is a plan view, Figure 1b shows a small part in section along line b-b of Figure 1; 1, FIGS. 1c and 1d are plan views showing part 2 of the carrier in the first and second embodiments at a very large magnification. The carrier 1 comprises a track 4 which is formed, for example, by a pre-formed groove. Track 4. is used to record the information signal. For this purpose, the record carrier 1 comprises a recording layer 6 which is deposited on the transparent material 5 and is covered with a protective coating 7. The recording layer is of a material which, when exposed to suitable radiation, shows an optically detectable structure change. Such a recording layer may be, for example, a thin metal layer such as tellurium. By exposure to laser radiation of sufficiently high intensity, the recording layer 6 can be locally melted so that it has a locally altered reflectance coefficient. When track 4 is tracked by a radiation beam whose intensity is modulated in accordance with the recorded information, an information combination of optically detectable record marks is obtained that is representative of the recorded information.

Alternatively, the recording layer 6 may consist of a variety of radiation-sensitive materials, for example magneto-optical materials, which are subjected to a structural change, for example from an amorphous to a crystalline structure, or vice versa. An overview of such materials can be found in Principles on Optical Disc Systems, Adam Hilgar Ltd., Bristol and Boston, p. 210-227.

By means of the preformed track 4, acting as a servo track, it is possible to achieve that the radiation beam directed at the carrier 1 exactly matches the track, which means that the position of the radiation beam 6 can be radially controlled by the radiation using the radiation reflected by the carrier 1. The measuring system for measuring the radial position of the irradiation spot on the carrier 1 may be any of the systems described in the above-mentioned Principles of optical disc systems.

In order to determine the position of the track section 4 with respect to the beginning of the track 4, a position information signal is recorded on the carrier 1 by means of a preformed track modulation 4, preferably in the form of a sine wave shown in FIG. Ic. However, other methods of modulating the track 4 are also suitable, for example the width modulation of FIG. Id. Since the wavy line of the track 4 can be easily formed in the manufacture of the carrier 1, this method is most suitable.

Further, in FIG. 1, the modulation of track 4 is shown to be exaggerated. In fact, the amplitude of the wavy line of about 3.10 <9 _m p _r i f a width of about 4 10 ^-6 m, which satisfies the reliable detection of the modulation-following radiation beam. The small amplitude of the wavy line has the advantage that the distance of adjacent tracks 4 can be small.

The preferred track modulation 4 is such that the track modulation frequency 4 is modulated in accordance with the position information signal.

Figure 2 shows an example of a suitable position information signal including position code signals 12 that can be shot with position synchronization signals 11. Each position code signal 12 may include a signal modulated by a two-phase mark having a length of 76 channel bits, the signal representing a code, a position information of 38 code bits. In a biphasic-modulated signal, each code bit is made up of two consecutive channel bits. Each code of the first logical value, in the present example 0, is made up of two bits of the same logical value. The second logical value, 1, is formed by two channel bits of different logical values. In addition, the logical value of the biphasic-modulated signal varies after each pair of channel bits (see FIG. 2), so that the maximum number of consecutive bits of the same logical value is a maximum of two. The position synchronization signals 11 are selected such that they can be distinguished from the position code signals 12. This is achieved by selecting the maximum number of consecutive bits of the same logical value in the position synchronization signals 11 equal to three. The position information signal shown in FIG. 2 has a frequency spectrum that contains barely any low frequency components. The advantage of this will be explained below.

Figure 2A shows in a very simplified and schematic manner the physical formation of a wavy track on a carrier of the invention for use in a recording apparatus according to the invention. As shown in the upper part of FIG. 2A showing again a substantial portion of FIG. 2, the code combinations in both the synchronization and position information combinations comprise a series of first signal levels 801 and second signal levels 802. whose combinations have the meaning explained with respect to FIG. 2. Each signal level 801 and 802 corresponds to a different ripple frequency formed along track A-. As shown in FIG. 2A, the waves have a first predetermined period E 1 in the first portions 901 corresponding to the first signal level 801 and a second predetermined period p ₂ in the second portions corresponding to the second signal level 802. In the lower part of FIG. 2A schematically illustrates only five wines for each channel bit, i.e., five wines for the second signal level 802 and for the first signal level 801, followed by fifteen waves of the second signal level 802 representing the three-bit channel bit synchronization mark. In practice, the number of periods pj and p ₂ in each channel bite course neporovnateíne larger, ie as corresponding to below the rate of channel bits in relation to the period Central track modulation between 54.10 ~ 64.10 ^{6 mA "6} m.

As mentioned above, the position information signal represents 38 bits of the position information code. The 38 bits of the position information code may include a time code indicating the time required to cover the distance from the beginning of the track £ to the position where the position information signal is located during a scan at a normal scan rate. Such a location information code may comprise, for example, a series of consecutive bits, as used, for example, when recording information with EFM on CD-Audio and CD-ROM discs. Figure 3 shows a position information code that is similar to the absolute time code used for CD-Audio and CD-ROM and which includes a first BCD-coded portion 13 indicating time in minutes, a second BCD-coded portion 14 indicating time in seconds, a third BCD a coded portion 15 indicating a subcode number and a fourth portion 16 comprising a series of parity bits for error detection.

Such a position information code for indicating the position in the track 4 is advantageous if the EFM modulated signal is to be recorded in accordance with the CD-Audio or CD-ROM standard. In this case, the absolute time codes present in the Q-channel of the subcode are of the same type as the position information code formed by track modulation 4.

In the case of a carrier intended for recording signals with EFM modulation in accordance with the CD-Audio or CD-ROM standard, it is preferable that for the normal viewing speed (1.2 to 1.4 ms ^-1 ), the mean frequency of the intensity modulation generated in the viewing radiation is beam modulation is equal to 22.05 kHz. That is, the mean period of modulation of track 4 is between 54.10 ^-6 m and 64.10 ^-6 m. In this case, the speed of the carrier 1 can be controlled very easily by comparing the phase of the detected modulation of the track 4 with the phase of the reference signal with a frequency that can be easily derived by dividing the frequency 4.3218 MHz (which is EFM bit rate). EFM signal recording. Furthermore, the frequency of the modulation of the track 4 lies outside the frequency band required to record the EFM signal, so that the EFM signal and the position information information signal practically do not cooperate during tracking. In addition, this frequency is located outside the frequency range of the drive system so that the drive is virtually unaffected by the modulation of track 4.

If the rate of channel bits of the position information information signal equal to 6,300 Hz is selected, the number of position information codes that can be read is 75 s ^-1 , which is exactly

-9 ^ equal to the number of absolute time codes per second of the recorded EFM signal. When, during recording, the phase of the subcode synchronization signal indicating the beginning of the absolute time code is coupled to the phase of the position synchronization signals formed by the track modulation 4, the absolute time indicated by the position information code remains synchronized with the absolute time codes in the recorded EFM signal.

Figure 11a shows the position of the recorded secondary code synchronization signals with respect to the portion of the track 4 modulated in accordance with the location synchronization signals 11 when the phase ratio between the position synchronization signal and the auxiliary code synchronization signal is kept constant during recording. The portions of the track 4 modulated in accordance with the synchronization signals 11 are denoted as parts 140. The positions in which the subcode synchronization signals are recorded are denoted as positions 141. As can be seen from FIG. 11a, the time indicated by the position information code remains synchronized with the time indicated by the absolute time code. If at the beginning of the recording the initial value of the absolute time code is adapted to the position information code, the position of the track 4 indicated by the absolute time code will always be the same as the position of the track 4 indicated by the position information code. This has the advantage that both the absolute time code and the position information code can be used to locate certain parts of the recorded signal.

If the positions 141 in which the subcode synchronization code is recorded locally coincide with the portions 140 of the track 4 that are modulated in accordance with the position information signals as shown in FIG. 11b, the difference between the positions of the track 4 represented by the position information code and the absolute time code will be minimal. Thus, it is desirable to minimize the phase difference between the position synchronization signals and the subcode synchronization signals during recording.

During EFM signal reading, the EFM channel clock signal is recovered from the read signal. When the recorded EFM signal is read, the clock signal of the EFM signal should be achievable as soon as the first subcode frame with useful information is read. This can be achieved, for example, by adding one or more dummy information EFM blocks to the beginning of the EFM signal. This method is particularly suitable for recording an EFM signal in a completely clean track 4.

However, if the EFM signal is to be recorded following the previously recorded EFM signal, it is advisable to position in track 4 where the recording of the new EFM signal is to start, substantially identical to the position where the recording of the previously recorded signal ended. Since in practice the precision with which the start and end can be placed is of the order of a few EFM frames, there will be either a small portion of the clear track between the sections of track 4 in which the signals are recorded or the first and second signals overlap one another.

Such an overlap or a portion of the clean track 4 results in the channel clock signal being recovered. Thus, it is preferred to select the interface 144 between the two recorded signals 142 and 143 such that it is located in the region between the portions 141 of the track 4, as shown in FIG. 11c. Thus, the section from the interface 144 to the beginning of the first subcode frame containing the useful information is long enough to ensure that the channel clock signal is restored before the beginning of the first subcode frame containing the useful information. Preferably, the position of the interface 144 is selected such that it is located in front of the center between the portions 140a and 140b of the track 4, since in this case a relatively long time is available during which the recovery of the channel clock signal can be safely performed. However, the interface 144 should be located sufficiently far from the end of the last subcode frame containing useful information of the recorded EFM signal 142 (this end corresponds to position 141a) to avoid overwriting the last complete frame of the subcode EFM signal 142 and thus breaking the last piece of information in the last frame. the secondary code of the EFM signal 142 due to inaccuracies in the start position setting of the EFM signal 143.

In addition to the destruction of the recorded information, such an overlap also results in the absolute time code corresponding to the last subcode frame and the end of the subcode synchronization signal no longer being reliably read. Since the absolute time code and subcode synchronization signals are used to control the reading process, it is desirable that the number of unreadable secondary code synchronization signals and absolute time code signals is minimal. It will be appreciated that the recorded information of the EFM signal 142 between the position 141a and the interface 144 cannot be read reliably. It is therefore advantageous to record fictitious information in this field, for example EFM pause code signals.

Figure 4 shows a recording and reading device 50 according to the invention by which the EFM signal is recorded so that the position synchronization signals 11 represented by the track modulation 4 remain synchronized with the subcode synchronization signals in the recorded EFM modulation signal. The device 50 comprises a drive motor 51 for rotating the carrier 1 about an axis 52. In contrast to the rotating carrier 1, an optical read / record head 53 of the conventional type is disposed. The read / write head 53 comprises a laser for producing a radiation beam 55 which is focused to create a small irradiation spot on the carrier 1.

As shown in FIG. 4, the recording head 53 has its pre-recorded signal detector (not shown) connected to the demodulation circuit 65 through the bandpass filter 56. The demodulation circuit is provided with an output 652 of the position synchronization codes and an output 650 of the position information signal. Output 652 is coupled via signal line 68 to input 653 of control unit 200, and output 650 of demodulation circuit 65 is coupled via bus 66 to input 651 of control unit 200. Controller 200 is further provided with output 100 of timing synchronization codes provided over signal line from modulation EFM modulation circuit 64. Said control unit further comprises a phase comparator 67 connected to the time synchronization code input 100 and the position synchronization code input 653. The phase comparator 67 is further provided with an output 300 coupled through an EXCLUSIVE-OR exclusive sum gate 61, a frequency divider, and a phase detector 60 with an excitation circuit 99 for generating an excitation signal for the drive motor 51.

The clock signal generation circuit 63 has a first output coupled to the clock input of the information modulation circuit 64 to be recorded. The second output of the clock generation circuit 63 is coupled through the EXCLUSIVE-OR exclusive frequency gate 61 and the frequency divider 62 to the first input of the phase detector 60. The second input of the phase detector 60 is coupled through the band pass filter 56, monostable level 57 circuit. the EXCLUSIVE-OR sum and the frequency divider 59 to the optical recorder detector.

The modulation circuit 64 has an input 400 coupled via a counter 69 and a bus 71 to a control unit 200, which is itself coupled via its input 651 via a bus 66 to a position information code output 650 output from the demodulation circuit 65.

It will be apparent to those skilled in the art that exclusive summing gates 58.61, frequency splitters 62.69, bandpass filter 56, monostable circuit 57, and counter 69 are not essential to the invention and that substantial joints of parts of the device of the invention can be realized as defined in the claims.

The read / write head 53 may operate in two modes, a read mode in which the laser produces a radiant beam of constant intensity that is not capable of causing an optically detectable change in the recording layer 6 and in a recording mode in which the beam 55 is modulated in depending on the information signal to be recorded to form a combination of recording marks having modified optical properties and corresponding signals Vi in the recording layer 6 at the locations of the track 4.

The recording and reading device 50 includes a conventional type of shifting means that keeps the radiation spot generated by the radiation beam 55 centered on the track 4. When tracking track 4, the radiation beam 55 is modulated by modulation of track 4. The read / write head 53 detects and generates a detected detection signal Vd representing the detected modulation.

A bandpass filter 56 having a mean frequency of 22.05. kHz, a frequency component modulated in accordance with the position information signal and generated by track modulation 4 is extracted from the detected signal. By means of a shaping circuit, for example a level-controlled monostable circuit 57, the bandpass filter output signal 56 is converted to a binary signal. -OR supplies frequency divider 59. The output of the frequency divider 59 is connected to one input of the phase detector 60. The 22.05 kHz frequency reference signal generated by the clock generator 63 is fed through the gate EXCLUSIVE-OR to the frequency divider 62. The output of the frequency divider 62 is connected to the second input of the phase detector 60. A signal proportional to the phase difference of the two input signals of the phase detector 60 is supplied as an excitation signal to the drive circuit 99, which is the power source for the drive circuit 51. speed, which minimizes the detected phase difference, which is a measure of speed variation.

The bandwidth of this control system is small, of the order of about 100 Hz compared to the bit rate of the 6,300 Hz position information signal. In addition, the position information signal which modulated the frequency of the track modulation 4 does not contain any low frequency components, so that the frequency modulation does not affect the rate control and the tracking speed is therefore maintained at a constant value for which the middle frequency of the frequency components formed in the detected signal Vd by the track modulation. 4 is maintained at 22.05 kHz, which means that the tracking rate is maintained at a constant value between 1.2 and 1.4 ms -1.

For recording, the device 50 comprises a modulation circuit 64 for modulating an EFM of the conventional type that converts the input information to a Vi signal modulated in accordance with the CD-ROM standard, or

CD-Audio. The EFM signal Vi is applied to the write / read head via a suitable modulator 71b which converts the EFM signal into a pulse sequence such that a combination of record marks corresponding to the EFM signal Vi is recorded in track 4. A suitable modulator 71b is known, for example, from U.S. Pat. The EFM modulation circuit is controlled by a control signal with a frequency of 4.3218 MHz equal to the EFM bit rate. The control signal is generated by the clock generation circuit 63. The 22.05 kHz reference signal, which is also being generated by the circuit 63, is derived from a 4.3218 MHz frequency division signal so that a fixed phase relationship is established between the control signal of the modulation modulation circuit 64 for EFM modulation and the 22.05 kHz reference signal. Since the control signal for the EFM is phase-coupled to the 22.05 kHz control signal, the tele signal Vd is also phase-coupled to the 22.05 kHz reference signal so that the absolute time codes generated by the EFM remain synchronized with the position information codes represented by by modulating track 4 that is being tracked. However, if the carrier 1 has blemishes, such as scratches, broken-out spots, etc., this may be a reason to increase the phase difference between the position code signals and the absolute time codes.

To suppress this phenomenon, the phase difference between the subcode synchronization signals generated by the modulation circuit 64 and the position synchronization signals that are sensed is determined and the tracking speed is corrected depending on the phase difference thus determined. For this purpose, a demodulation circuit 65 is used which extracts the position synchronization signals and the position code signals from the bandpass filter output signal 56 and restores the position information signal codes from the position code signal.

The demodulation circuit 65, described in detail below, feeds the position information signal codes to the microcomputer of the control unit 200 of the conventional type via the bus 66. In addition, the demodulation circuit 65 transmits a detector pulse Vsync to the signal line 68 indicating the moment the position synchronization signal was detected. . Modulation circuit 64 of modulation

The EFM 15 includes conventional means for generating the secondary code signal and for composing it with other information with EFM modulation. The absolute time codes may be generated by the counter 69 and may be transmitted via the bus 69a to the modulation modulation circuit 64 of the EFM. The read value of counter 69 is increased in response to control pulses at a frequency of 75 Hz. The control pulses for counter 69 are responses from the control signal 4.3218 kHz by frequency division via the EFM modulation modulation circuit and are applied to the read input of counter 69 by line 72a.

In addition, the EFM modulation circuit 64 generates a Vsub signal. which indicates the time at which the synchronization signal of the secondary code synchronization is generated. The signal Vsub is fed via line 70 to the microcomputer of the control unit 200. The counter 69 has inputs for reading the values converted to these inputs. The read inputs are connected to the microcomputer of the control unit 200 by the bus 71. It is also possible to insert the counter 69 into the microcomputer of the control unit 200.

The microcomputer of the control unit 200 is provided with a program to adjust the read / write head 53 relative to the desired location of the track 4 before recording. The position of the read / write head 53 relative to the desired location of the track 4 is determined by the position information signal codes generated by the demodulation circuit 65 and the read / write head 53 is moved in a radial direction depending on the position thus determined until it reaches the desired result position. The device comprises the usual means for moving the read / write head 53 in the radial direction, for example a motor 76 controlled by the microcomputer of the control unit 200 and a spindle 77. Once the desired track section 4 is reached, the read start of the counter 69 is set. Now, the read / write head 53 is put into the microcomputer of the control unit 200 via line 71a into record mode, and the modulation circuit 64 is triggered by a signal from the record start line 72, wherein the absolute time code recording in EFM the signal is kept synchronized in the same manner as explained above with the position code signal represented by track modulation 4. This has the advantage that the recorded absolute time codes always correspond to the position code signals represented by track modulation 4 in its region in which they are recorded. absolute time codes. This has a particular advantage if different information signals have been recorded consecutively, since the absolute time signals do not cause any step changes in the transition between two consecutive EFM signals. Thus, it is possible to utilize both the absolute time codes recorded together with the information signal and the position code signals represented by the modulation of track 4 to locate certain signal portions, giving a highly flexible working system.

Figure 7 illustrates the combination of the recording marks 100 formed when recording the EFM signal Vi in track 4. It should be reiterated that the track motion bandwidth bandwidth is significantly less than the tracking beam modulation frequency produced by track 4 modulation (in this case wavy line) on track A), so that the motion control of track 4 does not respond to disturbances of track 4 caused by its undulation. The tracking light beam thus does not define precisely track 4, but will follow a straight path, corresponding to the central position of the center track 4. The amplitude of the wavy track 4, however small, preferably of the order of 30.10 ^-9 m, which corresponds to the distance between the peaks of 60.10 ^"9 m, compared with track width 4 of the order of 10 ^-6 m, so that the combination of recording marks 100 is always substantially in the center of track 4. It should be noted that for clarity, the rectangular waveform of track 4 is shown. In practice, however, a sinusoidal wavy line is preferred. as explained in detail in FIG. 2A, since the RF components in modulation of the tracking beam 55 produced by the modulation of track 4 are reduced to a minimum so that the read EFM signal is affected to a minimum.

During recording, the microcomputer of the control unit 200 executes a program to derive from the Vsync and Vsub signals supplied by lines 68 and 70 the time interval between the time at which the synchronization signal is detected in the track section 4 and the second code synchronization signal. If the position synchronization signal precedes the subcode synchronization signal by more than a predetermined threshold value, the microcomputer of the control unit 200 transmits one or more additional pulses by line 73 to the frequency divider 59 through the exclusive sum gate 58 after each detection of the synchronization signal, causing the difference The phase detection detected by the phase detector 60 increases and the drive circuit 99 is influenced to reduce the speed of the drive motor 51, so that the phase difference between the detected position synchronization signals and the generated secondary code synchronization signal is reduced.

In case the detected synchronization signal differs from the generated secondary code synchronization signal by more than a prescribed threshold value, the microcomputer of the control unit 200 transmits additional pulses to the frequency divider 62 via line 74 through the exclusive sum gate 61. This causes a reduction in the phase difference detected by the phase detector, resulting in an increase in the speed of the drive motor 51 and a decrease in the phase difference between the detected secondary code signals. In this way, constant synchronization between the two synchronization signals is maintained. It should be noted that in principle it is also possible to use the recording rate instead of the read rate to maintain the desired phase ratio. This is possible, for example, by using the frequency of the EFM modulation control signal 64 depending on the detected phase difference.

Figure 5 is a flowchart of a suitable program to maintain synchronization. The program comprises a step S1, in which the time interval T between the time of detecting the read synchronization signal Td and the time of creating the secondary code synchronization signal To is determined in response to the signals Vsub and Vsync in lines 68 and 70. is greater than the prescribed threshold Tmax. If larger, step S3 is performed in which an additional pulse is sent to counter 62. After step S3, step S1 is repeated.

However, if the time interval T thus determined is less than Tmax, step S4 follows to determine if the time interval T is less than the minimum threshold value Tmin. If smaller, step S5 is performed in which an additional pulse is sent to counter 59. After step S5, step S1 is repeated. If it is determined during step S4 that the time interval is not less than Tmin, no additional pulse is generated and the program proceeds to step S1.

Figure 12 shows a flowchart of a program suitable for the microcomputer of the signal recording controller 200 following the previously recorded EFM signal. The program comprises a step S10 in which a position information code AB is determined which indicates a position that represents the end of the previously recorded information. This location information code may be stored in the memory of the microcomputer, for example after recording an earlier signal. In addition, at step S10, the position information code AB is derived from the number of subcode frames to be recorded, which code indicates the position where the recording is to end. This information may be generated, for example, by a storage medium in which the information to be recorded is stored and fed to the microcomputer of the control unit 200. This storage medium and the method of detecting the length of the signal to be recorded are outside the scope of the invention and hereafter described. After step S10, a step S11 is performed in which the read / write head 53 is positioned in the usual manner against the section of track 4 that precedes the point at which the recording of the EFM signal is to begin. A control means suitable for this purpose is described in detail in, for example, U.S. Pat. 4,106,058.

Further, at step S111, the detected detection signal Vsync, which outputs the demodulation circuit 65 through line 68, indicates that the newly read position information code is fed to the bus 66. In step S12, this position information code is read and in step S13 it is determined the read position information code corresponds to the position information AB, which indicates the start point of the recording. If not, then step by step

S13 follows the Force step. The program loop comprising the steps S111, S12 and S13 is repeated until the position information code read corresponds to the position information AB code. Then, at step S14, the initial value of the absolute time code in the counter 69 is brought into accordance with the position information code AB. Next, in step S5, the EFM modulation circuit 64 is actuated via line 72.

In step S16, the delay Td, which corresponds to the displacement of the scanning point over a distance corresponding to the distance SW between the interface 144 and the previous part 140 of the track 4 of FIG. 11c. At the end of the delay Td, the position of the scanning point in the track 4 corresponds to the desired recording starting position, and the read / write head 53 enters the recording mode at step S17, and then recording starts. Subsequently, each subsequent detection pulse Vsync is expected at step S18, and then, at step S19, it is determined whether the read position information code corresponds to the position information code AB, which indicates the end of the record. In the event of a mismatch, the program proceeds to step S18, and in the case of compliance, the delay Td is monitored in step S21, followed by step S22. In it, the read / write head 53 is put back into read mode. In the next step S23, the modulation circuit 64 for modulating the EFM is disabled.

The above-described method of determining track positions 4 indicating the beginning and end of the recording uses pre-recorded position information codes. It should be noted, however, that it is not necessarily necessary to determine location information codes to detect start and end positions. By reading the pre-recorded position synchronization signals, for example from the beginning of track 1, it is also possible to determine the position of the section of track 4 to be tracked.

Figure 6 shows the demodulation circuit 65 in detail. The demodulation circuit 65 includes a frequency modulation demodulator 80 that restores the position information signal from the bandpass output signal 56. The channel clock signal recovery circuit 81 restores the channel clock signal from the restored position information signal.

The position information signal is further utilized by feeding it to a comparator 82 which converts this signal into a binary signal that is fed to an eight-bit shift register 83 which is controlled by a channel clock. The parallel outputs of the shift register 83 are routed to a synchronization signal detector 84 which detects whether the bit pattern stored in the shift register 83 corresponds to a position synchronization signal. Serial output of shift register 83 is provided to the two-phase mark demodulator 85 to recover the code bit of the position information code represented by the position code signal modulated by the two-phase marks. The recovered code bits are fed to a shift register 86 which is controlled by a clock frequency equal to half the frequency of the channel clock signal and having a length equal to 38 bits of the position code signal.

The shift register 86 consists of a first part 86a of 14 bits and a second second part 86b of 24 bits.

The parallel outputs of the first part 86a and the second part 86b are connected to the error detection circuit 87. The parallel outputs of the second portion 86b are coupled to a register 88 with both parallel input and output.

The position information code is reset as follows: As soon as the synchronization signal detector 84 detects the presence of a bit pattern corresponding to the position synchronization signal, a detection pulse is generated in the shift register 84 which is applied to the pulse retarder 90 by line 89. the time corresponding to the processing time of the two-phase marker modulator, so that after the detection signal from the line 68 appears at the output of the deceleration circuit 90, a position information code is present in the shift register 86. A delayed detection pulse at the output of the pilot circuit 90 is also applied to the register

88, so that 24 bits representing the position information code are input to register 88 in response to the delayed detection pulse. The location information code input to register 88 is outputted by register 88, the outputs of which are connected by bus 66 to the microcomputer of control unit 200. Error detection circuit 87 is also activated by delayed detection pulses at the output of deceleration circuit 90, the location information is reliably in accordance with the usual detection criteria. The output signal that indicates whether the position information is reliable is fed to the microcomputer by the control unit 200 via line 91.

Figure 8 shows an embodiment of an apparatus 181 for manufacturing a carrier 1 according to the invention. The device 181 comprises a rotary table 182 which is rotated by a drive 183. The rotary table 182 carries a disc-shaped carrier 184, for example of glass, provided with a radiation-sensitive layer 185, for example a photoresist.

The laser 186 forms a light beam 187 that is projected onto the radiation sensitive layer 185. The light beam 187 first passes through the deflector. The deflector is of a type which deflects the light beam very precisely within a narrow range. In the present example, it is an acousto-optical modulator 190. The deflection apparatus may also be formed by other instruments, for example a low-angle mirror or an electro-optical deflection apparatus. The deflection range limits are indicated by the dashed line in FIG. The light beam 187 deflected by the acousto-optical modulator 190 passes through the optical head 196. The optical head 196 is movable radially relative to the rotatable carrier 184 by the actuator 199.

By the optical system described above, the light beam 187 is focused to form a tracking point 102 dependent on the deflection of the light beam 187 by the acousto-optical modulator 190 and in the radial position of the optical head 196 relative to the carrier 184. In the shown position of the optical head 196 the tracking point 102 can be moved in range BI acoustic-optical modulator.

190. Under the action of the optical head 196, the tracking point 102 may be guided in the range B2 for a given deflection.

The device 181 comprises a control apparatus 101, which may, for example, comprise the system described in detail in Dutch patent application 8701448 (PHN12.163). The control device 101 controls the drive speed 183 and the radial speed of the control device 199 such that the radiation-sensitive layer 185 is sensed at a constant speed along the radial path by the light beam 187. The device 181 further comprises a modulation circuit 103 for generating a periodic control signal. modulated in accordance with the position information signal. The modulation circuit 103 will be described in detail below. The control signal generated by the modulation circuit 103 is applied to a voltage-controlled oscillator 104 that generates a periodic control signal for the acoustic-modulator 190, the frequency of which is substantially proportional to the level of the control signal. The deflection generated by the acoustic-modulator 190 is proportional to the frequency of the control signal such that displacement of the sensing point 102 is proportional to the level of the control signal. The modulation circuit 103, the voltage-controlled oscillator 104, and the acoustic-optical modulator 190 are adapted to each other such that the amplitude of the periodic radial displacement of the point of interest is modulated

102 is approximately 30.10 ^-9 m. Besides that

103 and the control circuit 101 are relative to each other that the ratio of the center frequency of the control signal and the scanning speed of the radiation sensitive layer 185 is between 22050 / 1.2 m 2 and 22050 / 1.4 m ² , meaning that in each period of the control signal the displacement of the radiation sensitive layer 185 relative to the viewing point 102 is between 54.10 ^-6 m and 64.10 ⁶ m.

When the radiation-sensitive layer 185 has been subjected to radiation beam tracking as described above, it is subjected to an etching process to remove portions that have been exposed to light beam 187 to obtain a master disk. In this disc, a groove is provided having a periodic radial wavy line, the frequency of which is modulated in accordance with the position information signal. From this master disc, copies are made on which the recording layer 6 is stored. On carriers of the type described so obtained, the part corresponding to that part of the master disc from which the light-sensitive layer 185 has been removed is used as a track 4 which can be formed as groove or ridge. The method of manufacturing a carrier on which the track 4 corresponds to that portion of the master disc from which the radiation sensitive layer 185 has been removed has a very good reflectance of the track 4 at the rear and hence a favorable signal to noise ratio during reading of the carrier. The track 4 then corresponds to the highly smooth surface of the carrier 184, which is generally made of glass.

Figure 9 shows an example of a modulation circuit 103. The modulation circuit 103 comprises three cascade-connected cyclic eight-bit BCD counters 110, 111 and 112. Counter 110 is eight-bit and has a reading range of 75. When its maximum reading is reached, it sends a clock pulse to the counter input. 111. which is used as a second counter. When its read maximum 59 is reached, counter 111 sends a clock pulse to the counter input 112, which serves as a minute counter. The read values of the counters 110, 111 and 112 are fed via their parallel outputs via the buses 113, 114 and 115 to the circuit 116 to form fourteen parity bits for error detection in the usual manner.

The modulation circuit 103 further comprises a 42-bit shift register 117 divided into five successive sections 117a to 117e. The bit pattern 1001 ”is applied to four parallel inputs of the four-bit section 117a. wherein the bit pattern is converted to a position synchronization signal 11 in the manner described below during the modulation of the two-phase mark. Sections 117b, 117c and 117d each have 8 bits in length and section 117e are 14 bits in length. The read value of the counter 112 is supplied by the bus 115 to the parallel inputs of section 117b. The read value of the counter 111 is supplied by the bus 114 to the parallel inputs of section 117c. The read value of the counter 110 is applied to the parallel inputs of section 117d by the bus 113. Fourteen parity bits generated by the circuit 116 are fed by the bus 116a to the parallel inputs of the section 117b.

The serial shift register output signal is applied to a two-phase mark modulator 118. The output of the modulator 118 is fed to a frequency modulator 119. The modulation circuit 103 further comprises a clock circuit 120 for generating control signals for the counter 118, the shift register 117, the two-phase mark modulator 118, and the frequency modulator 119.

In the present example, the radiation sensitive layer 185 is monitored at a rate corresponding to said tracking speed of EFM modulated signals (1.2 to 1.4 ms ^-1 ) during the production of the master disc. The clock circuit 120 then produces a clock signal 139 with a frequency of 75 Hz for the counter 110. so that the read values of the counters 110, 111 and 112 still indicate the time elapsed while viewing the radiation sensitive layer 185.

Immediately after adapting the read values of the counter 110,

II and 112, the clock circuit 120 transmits the control signal 128 to the parallel input of the shift register 117, causing it to be filled in accordance with the signals applied to the parallel inputs, namely: bit combination 1001, read values of the counters 110,

III and 112 parity bits.

The bit pattern fed to the shift register 117 is fed to the two-phase mark modulator 118 via a serial output in synchronization with the clock signal 138 generated by the clock circuit 120. The clock 138 is 3150 Hz, so that the entire shift register is empty just as it is refilled from parallel inputs.

The two-phase marker modulator 118 converts 42 bits from shift register 117 into 84 channel bits of the position code signal. For this purpose, the modulator 118 comprises a clock-controlled bistable circuit 121 whose output logic level changes in response to a clock pulse on the clock input. The clock signals 122 are derived from the signals 123, 124, 125, and 126 generated by the clock circuit 120 and the serial output signal 127 of the shift register 170. The output signal 127 is applied to one input of the two-stage sum circuit 129.

The signal 123 is applied to the second input of the summation circuit 129. The output signal of the summation circuit 129 is applied to the clock input of the bistable circuit 121 through the product circuit 131. The signals 125 and 126 are applied to the inputs of the product circuit 131 whose output is connected to one 132. The output signal of the summation circuit 132 is also coupled to the clock input of the bistable circuit 121 via the product circuit 130.

The signals 123 and 124 contain two 180 ° phase shifted pulses of FIG. 10) with a frequency equal to the bit rate of signal 127, that is, 3,150 Hz, from shift register 117. Signals 125 and 126 contain negative pulses at a repetition rate of 75 Hz.

The phase of the signal 125 is such that a negative pulse of the signal 125 coincides with a second pulse of the signal 124 after the shift register 117 has been refilled. The negative pulse of the signal 126 is concurrent with the fourth pulse of the signal 124 after the shift register 117 has been refilled.

The position code signal 12 modulated by the two-phase markers at the output of the bistable circuit 121 is developed as follows: The signal pulses 124 are applied to the clock input of the bistable circuit 121 through the sum circuit 132 and the product circuit 130. 124. In addition, when the logic value is 1, an additional change in the logic signal value is obtained. In principle, synchronization signals are generated in a similar manner. However, the use of negative pulses of signals 125 and 126 prevents the second and fourth pulses of signal 124 from being fed back to the bistable circuit 121, thereby generating a position synchronization signal that can be distinguished from the signal modulated by the two-phase markers. It should be noted that this modulation method can lead to two different synchronization signals that are inverse to each other.

The position information signal obtained at the output of the bistable circuit 121 is fed to a frequency modulator 119 of a fixed ratio between the frequency at the output of the frequency modulator 26 and the bit rate of the position information signal. When the scan rate control is not disturbed, the subcode sync signals in the EFM signal remain synchronized with the position sync signals 11 in track 4 during recording of the EFM signal by the device 50. Speed control failures resulting from carrier imperfections can be compensated by very small corrections as explained Referring to FIG. 4th

In the frequency modulator 119 shown in FIG. 9, said advantageous relationship between the output frequencies and the bit rate of the position information signal is achieved. The frequency modulator 119 comprises a frequency divider 137 with a divisor 8. Depending on the logical value of the position information signal, a clock signal 134 having a frequency (27) (6,300) Hz or a clock signal 135 having a frequency (29) is fed to the frequency divider 137. 6,300) Hz to a frequency divider 137. For this purpose, the frequency modulator 199 is provided with a conventional multiplexing circuit 136. Depending on the logical value of the position information signal, the frequency 133 of the frequency modulator 29/8 is output. 6,300 = 22.8375 kHz or 27/8. 6,300 = 21.2625 kHz.

Since the frequencies of signals 134 and 135 are integral multiples of the channel bit rate of the position information signals, the length of one channel bit corresponds to an integer number of periods of the clock signals 134 and 135, which means that the phase steps in frequency modulation are minimal.

It should be noted that for the unidirectional component of the position information signal, the mean frequency of the frequency modulated signal is exactly 22.05 kHz, which means that rate control is only negligibly affected by frequency modulation.

A frequency modulator other than the modulator 119 shown in FIG. 9, for example, a conventional CPFSK modulator, as described, for example, in A. Bruce Carlson's book: Communications Systems, MacGraw Hill, p. 519 et seq.

It is advantageous to use a frequency modulator with a sinusoidal output signal. With the modulator 119 shown in FIG. 9, this can be achieved, for example, by arranging the bandpass filter between the output of the frequency divider 117 and the output of the modulator 119. The frequency oscillation is preferably of the order of 1 kHz.

The invention is not limited to the above embodiment. For example, in the described embodiment, the frequency spectrum of the position information signal has substantially no overlap with the frequency spectrum of the signal to be recorded. In this case, the position information signal recorded by the preformed track modulation may be distinguished from the subsequently recorded information signal. In the case of magneto-optical recording, the frequency spectra of the pre-recorded position information signal and the subsequently recorded information signal may overlap one another. During radiation beam tracking, modulation of the track results in modulation of the intensity of the radiation beam, while the information combinations created by the magnetic regions modulate the direction of polarization of the reflected radiation independently of the intensity of the modulation under the influence of the Kerr effect. In an embodiment of the invention described above, the tracking beam is modulated depending on the information to be recorded. In the case of magneo-optical recording, it is also possible to modulate the magnetic field instead of the tracking beam.

Claims (2)

A device for controlling the recording of information in a track of an optically readable record carrier comprising a radiation sensitive recording layer disposed on a disc-shaped substrate, the track having the shape of a preformed periodically wavy line comprising first portions in which the undulation has a first predetermined period; interchanged with second portions in which the ripple has a predetermined second period, the ripples with the first and second period being assembled along a track length into alternating combinations corresponding to a position information signal and a synchronization signal, characterized in that it comprises a circuit (63) for generating a clock signal, the output of which is connected to the clock input of the information recording modulation circuit (64), and further comprising a phase detector (60), the first input of which is connected to the second output of the clock signal generating circuit (63); The input of the phase detector (60) is connected to the output of the optical detector of the optical recording head (53) located on the path of the reflected portion of the recording beam (55), the output of the phase detector (60) connected to the other circuit (99) of the drive motor. (51) a record carrier (1). Device according to claim 1, characterized in that a demodulation circuit (65) with an output (652) of synchronization position codes connected to the control unit (200) is connected to the optical detector of the recording head (53) by its input. a time synchronization code input (100) and further comprising a phase comparator (67) coupled to the time synchronization code input (100) and a position synchronization code input (653), wherein the output (300) of the phase comparator (67) is coupled to the driver circuit (99). The apparatus according to the position demodulation circuit connected via the modulation circuit of claim 2, characterized in that (65) the information code output (650) has a control unit (200) with an input (400) (64) of the information to be recorded.